1. Field of the Invention
The present invention relates to handling of communication services, and in particular relates to methods for handling Packet Switched (PS) and Circuit Switched (CS) voice services in a service network or a mobile communication device that only supports one type of communication at one time.
2. Description of the Related Art
In a typical mobile communications environment, a user equipment (UE) may communicate voice and/or data signals with one or more service networks via cellular stations of the service networks. The wireless communications between the UE and the service networks may be in compliance with various wireless technologies, such as the Global System for Mobile communications (GSM) technology, General Packet Radio Service (GPRS) technology, Enhanced Data rates for Global Evolution (EDGE) technology, Wideband Code Division Multiple Access (WCDMA) technology, Code Division Multiple Access 2000 (CDMA 2000) technology, Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) technology, Worldwide Interoperability for Microwave Access (WiMAX) technology, Long Term Evolution (LTE) technology, and others.
Circuit switching is a telecommunications technology by which two network nodes establish a dedicated communications channel (circuit) before the nodes begin communicate. The circuit remains connected throughout the duration of the communications session. The circuit functions as if the nodes were physically connected as with an electrical circuit. Another type of telecommunication technology is Packet switching, where all transmitted data, regardless of content, type, or structure, are grouped into appropriate sized data blocks, called packets. Packet switching features delivery of variable-bit-rate data streams (sequences of packets) over a shared network. When traversing network adapters, switches, routers and other network nodes, packets are buffered and queued, resulting in variable delay and throughput depending on the traffic load in the network.
Different telecommunication networks employ different types of switching technologies and combinations thereof. In a legacy telecommunication network such as the GSM network, only the CS type of telecommunication technology is employed. In the GPRS and UMTS network, both the CS and the PS types are utilized for transmission. In the LTE network, only the PS type of telecommunication technology is implemented. Therefore methods are required to handle multiple PS and CS voice service for a mobile communication device which moves from one network that supports CS and PS voice services to another network that only supports one CS voice service.